There are three immediate reasons for learning more about the mechanisms of gastrointestinal fat digestion and adsorption: 1) the ability of certain dietary fats to promote atheroschlerosis is dependent upon the positional distribution of their constituent fatty acids; 2) high dietary levels of certain fats promote tumorogenesis in the skin, breast and colon; and 3) the intestinal absorption of hydrophobic (fat soluble) substances, many of which are carcinogenic and poorly absorbed, is somehow enhanced by the presence of dietary fat. We have recently visualized fat digestion under simulated physiological conditions and discovered that there is a persistent hydrocarbon domain throughout the digestive process. This domain, or space, remains intact during the enzymatic conversion of triglyceride to fatty acid and monoglyceride. Hydrophobic molecules that have been dissolved in the hydrocarbon domain during fat digestion flow from nondispersable triglyceride to the products of fat digestion which are dispersed by bile salts and absorbed. The concept of an uninterrupted hydrocarbon domain which can carry a wide variety of different molecules during fat digestion has profound significance for human health and disease. This concept explains how a large family of fat-soluble substances are dispersed in the intestine and thereby more efficiently absorbed. It offers a mechanism to explainfood chain magnification of DDT and other hydrophobic toxicants. It reveals how otherwise insoluble carcinogens can be absorbed in high concentrations and it represents a simple method of hydrophobic drug delivery. The immediate objective of the proposed research is to determine the quantitative and qualitative carrying capacity of the hydrocarbon domain in intact triglyceride and the product phases. Micro-visualization of the gastrointestinal disassembly of tissues, cells, and food particles will eventually yield an abundance of information on enzyme action, biological structure, and mechanisms of molecular dispersion. Thus, our long range objectives are to continue to develop techniques for exploiting this approach to the study of digestion.